An accurate guiding system suitable for obtaining precise movement of the carriage of a machine tool is disclosed in U.S. Pat. No. 3,578,827. In this arrangement, two bearings are carried by one component of the system and positioned adjacent two opposed walls of a second component with respect to which their is to be relative movement. One of the bearings is rigidly mounted on the first component and positioned adjacent one of the walls, which is made to an accurate dimension. The other bearing is adjacent the opposite wall and is connected by a spring to the first component. This provides the second bearing with freedom to float, so that as the components move relative to each other, the path of movement is controlled by the rigidly mounted bearing and the first wall as the second bearing floats to accommodate dimensional differences. The resulting system allows a very accurate and relatively long path of movement to be achieved at a reasonable expense.
There are certain limitations to the prior art construction, however. The use of a spring provides a varying force, not necessarily entirely uniform, as the bearing floats and the spring deflects. The bearing shoe has uniform loading on one side where the air is discharged at the bearing surface, while the other side has a point or localized load where it is engaged with the spring in one case or the rigid mounting means in the other. This means that the bearing shoe tends to deform, unless made quite heavy. Even then, some distortion is unavoidable. Deformation of the bearing can result in variation in the lift height accomplished by the air discharged through the bearing. Contact between the bearing and the wall may result if the lift height is too small, thereby resulting in failure of the bearing to perform its function. This design requires a relatively high degree of parallelism between the two opposed surfaces to avoid changes in the lift of the bearings and the risk of contact between a bearing and the adjacent surface.